U.S. patent application number 10/801466 was filed with the patent office on 2005-02-10 for inkjet ink set and method of using same.
Invention is credited to Bauer, Richard Douglas, Hermansky, Clarence Gaetano.
Application Number | 20050030360 10/801466 |
Document ID | / |
Family ID | 33131801 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050030360 |
Kind Code |
A1 |
Bauer, Richard Douglas ; et
al. |
February 10, 2005 |
Inkjet ink set and method of using same
Abstract
This invention pertains to an ink set for inkjet printing, in
particular to an ink set comprising at least one ink comprising
colorant and nonaqueous vehicle; and a fixing fluid comprising
fixing agent and aqueous vehicle. The invention also pertains to a
method of inkjet printing with this ink set.
Inventors: |
Bauer, Richard Douglas;
(Kennett Square, PA) ; Hermansky, Clarence Gaetano;
(Wilmington, DE) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
33131801 |
Appl. No.: |
10/801466 |
Filed: |
March 16, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60458483 |
Mar 28, 2003 |
|
|
|
Current U.S.
Class: |
347/95 ;
347/100 |
Current CPC
Class: |
B41M 5/0017 20130101;
B41M 7/0018 20130101; C09D 11/36 20130101; C09D 11/30 20130101;
C09D 11/40 20130101; C09D 11/54 20130101 |
Class at
Publication: |
347/095 ;
347/100 |
International
Class: |
C09D 011/02; B41J
002/17 |
Claims
1. An inkjet ink set comprising: a first ink comprising a colorant
in a nonaqueous vehicle; and a fixing fluid comprising a fixing
agent in an aqueous vehicle.
2. The ink set of claim 1, further comprising at least four
differently colored inks, at least one of the colored inks being a
first ink.
3. The ink set of claim 1, wherein the colorant in the first ink is
selected from the group consisting of a pigment and a dye.
4. The ink set of claim 1, wherein the colorant in the first ink is
a self-dispersing pigment.
5. The ink set of claim 1, wherein the nonaqueous vehicle has no
more than about 10% by weight of water based on the total weight of
the nonaqueous vehicle.
6. The ink set of claim 1, wherein the fixing agent is an ionizable
component.
7. The ink set of claim 2, wherein the colorant in the first ink is
selected from the group consisting of a pigment and a dye; the
nonaqueous vehicle has no more than about 10% by weight of water
based on the total weight of the nonaqueous vehicle; and wherein
the fixing agent is an ionizable component.
8. The ink set of claim 7, wherein the colorant in the first ink is
a self-dispersing pigment.
9. A method of inkjet printing a substrate comprising the steps of
jetting an ink set onto a substrate, the ink set comprising: a
first ink comprising a colorant in a nonaqueous vehicle; and a
fixing fluid comprising a fixing agent in an aqueous vehicle.
10. The method of claim 9, wherein the ink set further comprising
at least four differently colored inks, at least one of the colored
inks being a first ink.
11. The method of claim 9, wherein the colorant in the first ink is
selected from the group consisting of a pigment and a dye.
12. The method of claim 9, wherein the colorant in the first ink is
a self-dispersing pigment.
13. The method of claim 9, wherein the nonaqueous vehicle has no
more than about 10% by weight of water based on the total weight of
the nonaqueous vehicle.
14. The method of claim 9, wherein the fixing agent is an ionizable
component.
15. The method of claim 10, wherein the colorant in the first ink
is selected from the group consisting of a pigment and a dye; the
nonaqueous vehicle has no more than about 10% by weight of water
based on the total weight of the nonaqueous vehicle; and wherein
the fixing agent is an ionizable component.
16. The method of claim 15, wherein the colorant in the first ink
is a self-dispersing pigment.
17. The method of claim 9, wherein the fixing fluid is jetted onto
the substrate before the first ink.
18. The method of claim 9, wherein the area fill of the fixing
fluid is less than the area fill of the first ink.
19. The method of claim 17, wherein the area fill of the fixing
fluid is less than the area fill of the first ink.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.119
from U.S. Provisional Application Ser. No. 60/458,483 (filed Mar.
28, 2003), the disclosure of which is incorporated by reference
herein for all purposes as if fully set forth.
BACKGROUND OF THE INVENTION
[0002] This invention pertains to an ink set for inkjet printing,
in particular to an ink set comprising at least one nonaqueous ink
and at least one aqueous fixer fluid. The invention also pertains
to a method of inkjet printing with this ink set.
[0003] Inkjet printing is a non-impact printing process in which
droplets of ink are deposited on print media, such as paper, to
form the desired image. The droplets are ejected from a printhead
in response to electrical signals generated by a
microprocessor.
[0004] Ink can comprise colorant that is dissolved or dispersed in
the ink vehicle. The ink vehicle can be aqueous or nonaqueous and
the ink is referred to as aqueous or nonaqueous ink,
accordingly.
[0005] Aqueous ink is advantageous because water is especially
environmentally friendly. However, water is relatively volatile and
aqueous-based inks can dry out quickly on the printhead. Humectants
are often added to aqueous ink to retard drying, but precipitation
of formulation ingredients can occur as water is lost even if the
ink is not "dry". Also, images printed with colorants that are
dispersible/soluble in water tend to be prone to rub-off and smear.
Nonaqueous inkjet inks can be formulated with solvents having low
volatility (i.e. slow drying or non-drying) and can employ
colorants that provide highly rub- and smear-resist images. When
jetted on paper though, nonaqueous inks tend to penetrate deeply,
similar to penetrating aqueous inks, causing loss of color density,
blurring and strikethrough.
[0006] Penetrating aqueous inks are formulated with a vehicle that
penetrates rapidly into the printed substrate, and in so doing
becomes quickly dry to the touch and therefor appears "fast
drying". However, penetrating formulations also tend to move
outward as well as downward which results, as was already
mentioned, in blurring and strikethrough.
[0007] One way to reduce blurring and strikethrough in fast drying
aqueous inks is to apply a fixing solution to the media prior to
printing the ink. See, for example, U.S. Pat. No. 5,746,818, U.S.
Pat. No. 6,450,632, U.S. Ser. No. 20020044185 and EP1258510, and
commonly owned U.S. application Ser. No. 10/755,630 (filed Jan. 12,
2004, claiming priority from U.S. Provisional Application Ser. Nos.
60/440,493 (filed Jan. 16, 2003) and 60/449,760 (filed Feb. 25,
2003)), the disclosures of which are incorporated by reference
herein for all purposes as if fully set forth.
[0008] Fixers commonly operate by creating an adverse charge-charge
interaction with the colorant in the aqueous ink thereby
precipitating and fixing the colorant on the substrate surface.
This mechanism is effective with aqueous inks because the colorant
is typically stabilized to dispersion or solution by an ionic
mechanism. A fixer with opposite charge effectively destabilizes
and fixes the colorant. However, these methods of fixation are not
expected to be operable with nonaqueous inks because charge
stabilization is not in effect in a low dielectric constant
(nonaqueous) vehicle.
[0009] A need thus exists for fixer fluids that can improve the
image quality of nonaqueous inks.
SUMMARY OF THE INVENTION
[0010] In accordance with one aspect of the present invention,
there is provided an inkjet ink set comprising:
[0011] a first ink comprising a colorant in a nonaqueous vehicle;
and
[0012] a fixing fluid comprising a fixing agent in an aqueous
vehicle.
[0013] Preferably, the ink set comprises, in addition to the fixing
fluid, at least two differently colored inks, and more preferably
at least four differently colored inks (such as CMYK), at least one
of the colored inks being a first ink as described above. The inks
other than the first ink (and fixing fluid) are preferably
non-aqueous as well.
[0014] Preferably the fixing fluid when printed leaves no visible
marking and/or is substantially colorless.
[0015] In accordance with another aspect of the present invention,
there is provided a method of inkjet printing a substrate
comprising the steps of jetting an ink set onto a substrate, the
ink set comprising the ink set as set forth above.
[0016] In accordance with another aspect of the present invention,
there is provided a method of inkjet printing a substrate
comprising the steps of:
[0017] jetting onto an area of the substrate, in an area fill, a
fixing fluid comprising a fixing agent in an aqueous vehicle;
and
[0018] jetting onto at least a portion of the area fill of the
fixing fluid, a first ink comprising a colorant in a nonaqueous
vehicle.
[0019] Preferably the fixing fluid is jetted onto the substrate
before the first ink.
[0020] These and other features and advantages of the present
invention will be more readily understood, by those of ordinary
skill in the art, from a reading of the following detailed
description. It is to be appreciated that certain features of the
invention which are, for clarity, described above and below in the
context of separate embodiments, may also be provided in
combination in a single embodiment. Conversely, various features of
the invention that are, for brevity, described in the context of a
single embodiment, may also be provided separately or in any
subcombination. In addition, references in the singular may also
include the plural (for example, "a" and "an" may refer to one, or
one or more) unless the context specifically states otherwise.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] According to the present invention, a first ink comprising a
colorant, a nonaqueous vehicle and, optionally, other ingredients
such as surfactants, dispersants, binders and/or other additives
and adjuvants well-known in the relevant art, is applied to a
substrate in combination with a fixer (fixing) fluid comprising a
fixing agent in an aqueous vehicle. Preferably, the fixer fluid is
applied to the substrate first and then the ink is printed on top
of the applied fixer.
[0022] Colorant for Non-Aqueous Ink
[0023] The colorant can be soluble or dispersed in the ink vehicle.
Soluble colorants (such as dyes) are dissolved in the non-aqueous
vehicle, while insoluble colorants (such as pigments) are stably
dispersed.
[0024] Pigments, traditionally, are stabilized to dispersion by
dispersing agents, such as polymeric dispersants or surfactants.
More recently though, so-called "self-dispersible" or
"self-dispersing" pigments (hereafter "SDP(s)") have been
developed. As the name would imply, SDPs are dispersible in a
vehicle without dispersants.
[0025] Suitable dyes for inkjet applications are generally well
known. A representative selection of such dyes can be found, for
example, in U.S. Pat. No. 5,932,631 and U.S. SIR H1967, the
disclosures of which are incorporated by reference herein for all
purposes as if fully set forth. The exact choice of dyes will
depend upon the color reproduction and print quality requirements
of the application.
[0026] Dyes used in an aqueous ink vehicle are most commonly ionic
in character, which means they form an ionic (anionic or cationic
depending on the specific dye) chromaphore in aqueous solution.
Frequently, these dyes are only slightly soluble in a nonaqueous
vehicle. However, solubility in a nonaqueous vehicle can be
increased by association with an amphiphile (surfactant) of charge
opposite to the chromaphore. The amount of surfactant needed can be
readily determined by routine experimentation. Useful anionic
surfactants may include, for example, alkylbenzene sulfonates,
alkyl sulfates and higher alkyl ether sulfates, alkyl phosphates
alkyl sulfosuccinates, condensation products of naphthalene
sulfonic acids, and polyoxyethylene alkyl phosphates. Useful
cationic surfactants may include, for example, quaternary ammonium
salt type cationic surfactants or amine salt type surfactants.
[0027] Suitable pigments for inkjet applications are also generally
well known. A representative selection of such pigments are found,
for example, in U.S. Pat. No. 5,026,427, U.S. Pat. No. 5,086,698,
U.S. Pat. No. 5,141,556, U.S. Pat. No. 5,169,436 and U.S. Pat. No.
6,160,370, the disclosures of which are incorporated by reference
herein for all purposes as if fully set forth. The exact choice of
pigment will depend upon color reproduction and print quality
requirements of the application. The pigment may be black, such as
those based on carbon black, or may be colored such as those based
on cyan (e.g. PB 15:3 and 15:4), magenta (e.g. PR 122 and 123),
yellow (e.g. PY 128, 74 and 120).
[0028] Dispersants to stabilize the pigments to dispersion are
preferably polymeric because of their efficiency. Examples of
typical dispersants for nonaqueous pigment dispersions include, but
are not limited to, those sold under the trade names: Disperbyk
(BYK-Chemie, USA), Solsperse (Avecia) and EFKA (EFKA Chemicals)
polymeric dispersants.
[0029] Suitable pigments also include SDPs. SDPs for aqueous inks
are well known. SDPs for nonaqueous ink are also known and include,
for example, those described in U.S. Pat. No. 5,698,016, U.S. Ser.
No. 2001003263, U.S. Ser. No. 2001004871 and U.S. Ser. No.
20020056403, the disclosures of which are incorporated by reference
herein for all purposes as if fully set forth.
[0030] It is desirable to use small pigment particles for maximum
color strength and good jetting. The particle size may generally be
in the range of from about 0.005 micron to about 15 microns, is
typically in the range of from about 0.005 to about 1 micron, is
preferably from about 0.005 to about 0.5 micron, and is more
preferably in the range of from about 0.01 to about 0.3 micron.
[0031] The levels of pigment employed in the instant inks are those
levels that are typically needed to impart the desired OD to the
printed image. Typically, pigment levels are in the range of from
about 0.01 to about 10% by weight, based on the total weight of the
ink.
[0032] Nonaqueous Vehicle
[0033] "Nonaqueous vehicle" refers a vehicle that is substantially
comprised of a nonaqueous solvent or mixtures of such solvents,
which solvents can be polar and/or nonpolar. Examples of polar
solvents include alcohols, esters, ketones and ethers, particularly
mono- and di-alkyl ethers of glycols and polyglycols such as
monomethyl ethers of mono-, di- and tri-propylene glycols and the
mono-n-butyl ethers of ethylene, diethylene and triethylene
glycols. Examples of nonpolar solvents include aliphatic and
aromatic hydrocarbons having at least six carton atoms and mixtures
thereof including refinery distillation products and
by-products.
[0034] Even when no water is deliberately added to the nonaqueous
vehicle, some adventitious water may be carried into the
formulation, but generally this will be no more than about 2-4%. By
definition, the nonaqueous ink of this invention will have no more
than about 10%, and preferably no more than about 5%, by weight of
water based on the total weight of the nonaqueous vehicle.
[0035] Fixing Fluid
[0036] The fixing fluid comprises an aqueous vehicle and an
effective amount of one or more fixing agents. A fixing agent is an
ingredient that initiates a change in the solubility or stability
of the colorant and fixes the colorant in place in the printed
image. An "effective amount" of fixing agent is an amount that is
effective in achieving an improvement in strikethrough, OD, chroma
and/or bleed as compared to a print that has not been fixed.
[0037] One mechanism of fixation, though not necessarily the only
one, is interaction of fixing agent with a surfactant or dispersant
in the nonaqueous ink. Such fixing agents can be selected from
ionizable components such as polymers, surfactants, lattices (e.g.
dispersed polymers) and low molecular weight organic molecules
(mono- and multi-functional). Fixing agents include mono- or
multi-functional carboxylate or sulfonate salts that are soluble in
the aqueous vehicle, and polymer lattices such as acrylic and
polyurethane polymers that are dispersed in the aqueous
vehicle.
[0038] The fixing fluid is preferably formulated for high spread
and quick penetration and drying. To achieve these properties,
surfactants and/or penetrating solvents will typically be employed.
The surface tension is preferably less than about 40 mN/m.
Typically, the fixer fluid will contain about 0.1% to about 20%,
more preferably about 1.0 to about 15%, fixing agent based on the
total weight of the fixing fluid.
[0039] Aqueous Vehicle
[0040] "Aqueous vehicle" refers to water or a mixture of water and
at least one water-miscible organic solvent (co-solvent). Selection
of a suitable mixture depends on requirements of the specific
application, such as desired surface tension and viscosity, the
selected fixer, drying time of the fixer fluid, and the type of
substrate onto which an aqueous fixer fluid will be printed. If a
mixture of water and a water-soluble solvent is used, the aqueous
vehicle typically will contain about 30% to about 95% water with
the balance (i.e., about 70% to about 5%) being the water-soluble
solvent. Preferred compositions contain about 60% to about 95%
water, based on the total weight of the aqueous vehicle.
[0041] The aqueous vehicle can be made to be fast penetrating
(rapid drying) by including surfactants or penetrating agents such
as glycol ethers and 1,2-alkanediols. Glycol ethers include
ethylene glycol monobutyl ether, diethylene glycol mono-n-propyl
ether, ethylene glycol mono-iso-propyl ether, diethylene glycol
mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene
glycol mono-t-butyl ether, diethylene glycol mono-n-butyl ether,
triethylene glycol mono-n-butyl ether, diethylene glycol
mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol
mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene
glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether,
dipropylene glycol mono-n-butyl ether, dipropylene glycol
mono-n-propyl ether, and dipropylene glycol mono-isopropyl ether.
1,2-Alkanediols are preferably 1,2-C4-6 alkanediols, most
preferably 1,2-hexanediol. Suitable surfactants include ethoxylated
acetylene diols (e.g. Surfynols.RTM. series from Air Products),
ethoxylated primary (e.g. Neodol.RTM. series from Shell) and
secondary (e.g. Tergitol.RTM. series from Union Carbide) alcohols,
sulfosuccinates (e.g. Aerosol.RTM. series from Cytec),
organosilicones (e.g. Silwet.RTM. series from Witco) and fluoro
surfactants (e.g. Zonyl.RTM. series from DuPont). The amount of
glycol ether(s) and 1,2-alkanediol(s) added must be properly
determined, but is typically in the range of from about 1 to about
15% by weight and more typically about 2 to about 10% by weight,
based on the total weight of the fixer fluid. Surfactants may be
used, typically in the amount of about 0.01 to about 5% and
preferably about 0.2 to about 2%, based on the total weight of the
fixer fluid.
[0042] The amount of vehicle in the fixer fluid is typically in the
range of about 70% to about 99.8%, and preferably about 80% to
about 99.8%, based on total weight of the fixer fluid.
[0043] Other Ingredients
[0044] Other ingredients may be formulated into the inks and fixer
fluids used in accordance with this invention, to the extent that
such other ingredients do not interfere with the mutually
interactive (fixing) mechanisms of the ink set or the stability and
jetability of the ink. Such other ingredients are generally well
known in the art and include one or more of a biocide, e.g.
bactericide, fungicide, algicide and the like; sequestering agent;
buffering agent; corrosion inhibitor; light stabilizer; anti-curl
agent; thickener; defoamer, and the like, to improve various
properties or function of the ink or fixer compositions as
needed.
[0045] The amount of each ingredient must be properly determined,
but is typically in the range of from about 0.1 to about 15% by
weight, and more typically about 0.2 to about 10% by weight, based
on the total weight of the ink.
[0046] Binder may be also used and can be soluble or dispersed
polymer(s), added to the ink to improve the adhesion of a pigment.
Examples of polymers that can be used include polyesters,
polystyrene/acrylates, sulfonated polyesters, polyurethanes,
polyimides and the like. When present, soluble polymer is
advantageously used at levels of at least about 0.3%, and
preferably at least about 0.6%, based on the total weight of the
ink. Upper limits are dictated by ink viscosity or other physical
limitations.
[0047] Ink Set
[0048] A fixing fluid is an "ink" with fixing agent, but not
necessarily colorant. The fixing agent in the fixing fluid of the
instant invention serves to reduce colorant mobility. The fixing
fluid is preferably jetted from an inkjet printhead. For the
purposes of this invention, the fixing fluid is considered part of
the "ink set" although, for sake of convenience and clarity, the
term "ink" will generally be used herein to indicate an ink with
colorant but no fixing agent. The fixing fluid can, if desired,
contain colorant, but that may limit the application to the
fixation of black ink only. Preferably, the fixing fluid contains
substantially no colorant, and/or is substantially clear. Also,
preferably, the fixing fluid can be printed on the substrate and
leave no visible marking.
[0049] Preferably, the ink set comprises, in addition to the fixing
fluid, at least two differently colored inks, and more preferably
at least four differently colored inks (such as CMYK), at least one
of the colored inks being a first ink as described above. The
colorants in the inks of the ink set may all be dyes, pigments or
some combination thereof. Other than the first ink, which is
nonaqueous, the other colored inks in the ink set are preferably
also nonaqueous.
[0050] Ink Properties
[0051] Jet velocity, drop size and stability are greatly affected
by the surface tension and the viscosity of the ink. Ink jet inks
typically have a surface tension in the range of about 20 dyne/cm
to about 60 dyne/cm at 25.degree. C. Viscosity can be as high as 30
cP at 25.degree. C., but is typically somewhat lower. The inks have
physical properties compatible with a wide-range of ejecting
conditions, i.e., driving frequency of the piezo element, or
ejection conditions for a thermal head, for either a drop-on-demand
device or a continuous device, and the shape and size of the
nozzle. The ink set of this invention should have excellent storage
stability for long periods so as not clog to a significant extent
in an ink jet apparatus. Further, it should not alter the materials
of construction of the ink jet printing device it comes in contact
with, and be essentially odorless and non-toxic.
[0052] Although not restricted to any particular viscosity range or
printhead, the inventive ink set, because of the use of nonaqueous
inks, is particularly suited to lower viscosity applications such
as those required by printheads that jet small droplet volumes,
e.g. less than 10 pL. Thus the viscosity (at 25.degree. C.) of the
inventive inks and fixer can be less than about 7 cps, is
preferably less than about 5 cps, and most advantageously is less
than about 3.5 cps.
[0053] Method of Printing
[0054] The fixing fluid will typically be deposited on the
substrate before the nonaqueous ink, and preferably substantially
only in areas subsequently printed with the non-aqueous ink. The
area covered by the fixer (area fill) need not, however, entirely
fill the area printed with the non-aqueous ink. Also, the ink need
not fall (entirely) on top of the fixer. The area fill of
under-printed fixer can be substantially less than the area fill of
over-printed ink.
[0055] Substrate
[0056] The instant invention is particularly advantageous for
printing on plain paper such as common electrophotographic copier
paper.
EXAMPLES
[0057] Preparation of Magenta Pigment Dispersion
[0058] A magenta dispersion was prepared by mixing 1200 g of
Magenta PR122 pigment (Ciba), 1463 g of Disperbyk 2000
(BYK-Chemie), 2337 g of Dowanol DPM (dipropylene glycol methyl
ether) and milling in a media mill with 250 ml of 0.6-0.8 mm
zirconia media. After milling to the desired endpoint, the media
was separated and the dispersion was further diluted with Dowanol
DPM to a final pigment concentration of 18.4% by weight. The
viscosity was about 36 cps (Brokfield viscometer, 25.degree. C.)
and median particle size was 82 nm.
[0059] Preparation of Yellow Pigment Dispersion
[0060] A yellow dispersion concentrate was prepared by mixing the
following ingredients: 125 g of Yellow PY120 (Clarient), 208 g of
Disperbyk 161 (BYK-Chemie), 292 g of Dowanol PMA (propylene glycol
methyl ether acetate) and milling in a media mill with 1130 ml of
0.6-0.8 mm zirconia media. After milling to the desired endpoint,
the media was separated and the dispersion was further diluted with
Dowanol PMA to a final pigment concentration of 20.0% by weight.
The viscosity was about 26.5 cps (Brokfield viscometer, 25.degree.
C.) and median particle size was 132 nm.
[0061] General Procedure for Preparation of Acrylic Dispersion
Binder
[0062] The acrylic dispersed binder can be prepared as follows. A
solution prepared from deionized water (1318.0 gm), nonylphenoxy
polyethyleneoxy ethyl sulfate (4 moles EO) (5.0 g) and allyl
dodecyl sulfosuccinate sodium salt (7.0 gm) is added to a reaction
vessel equipped with a heating mantle, stirrer, thermometer, reflux
condenser and two addition funnels. The resulting mixture is heated
to 85.degree. C. with mixing. A solution comprising deinoized water
(40.0 g) and ammonium persulfate (4.0 g) is placed in an addition
funnel attached to the reactor. A second solution comprised of
methyl methacrylate monomer (MMA) (576.0 gm), styrene monomer (Sty)
(240.0 gm), 2-ethyl hexyl acrylate monomer (2-EHA) (640.0 gm),
N-methylol methacrylamide monomer (MOLMAN) (87.0 gm), methacrylic
acid monomer (MAA) (48.0 gm), nonylphenoxy polyethyleneoxy ethyl
sulfate (14.0 gm), allyl dodecyl sulfosuccinate sodium salt (20.0
gm) and deionized water (908.0 gm) is emulsified with an Eppenbach
homogenizer. This pre-emulsified solution is placed in an addition
funnel attached to the reactor. Five percent of the resulting
pre-emulsion is added to the reaction vessel and the temperature of
the constituents in the vessel is stabilized at 85.degree. C. The
ammonium persulfate solution is then added and held for 5 minutes.
The remainder of the pre-emulsion is added over a period of 90
minutes at a uniform rate. The temperature of the resulting
polymerization mixture is maintained at 88-90.degree. C. during the
addition. The polymerization mixture is held at this temperature
for about 1 hour. The polymerization mixture is cooled to
35.degree. C. and neutralized with a solution of deionized water
(30.0 gm), aqueous ammonium hydroxide solution (45.0 gm) and (29%
aqueous solution) of
methanol((((2-dihydro-5-methyl-3(2H)-oxazolyl)-1-met-
hylethoxy)methoxy)methoxy) (4.0 gm) to achieve a pH of 8.5 to
9.0.
[0063] The resulting dispersed polymer will have the following
composition: MMA/S/2-EHA/MOLMAN/HEA/MAA in a weight ratio of
36/15/40/3/3/3. The polymer typically will have a weight average
molecular weight of about 500,000-1,250,000. The dispersed polymer
average particle size typically is about 0.095 microns and percent
weight solids is adjusted to about 35.7%.
[0064] Ink Preparation
[0065] The ink formulations are given in the following tables. Ink
A and Ink B were prepared by diluting an ink concentrate with
solvent to effect a pigment concentration of 3 percent, by weight.
Ink C was prepared by adding Acid Blue 40 (anionic) dye to the
components shown, using cetyl trimethyl ammonium bromide to achieve
solubilization of the dye in the nonaqueous vehicle. Values are in
weight percent of the final ink weight.
1 Ink Formulations Ingredients Ink A Ink B Ink C Dispersion 1 (as %
pigment) -- 3.0 -- Dispersion 2 (as % pigment) 3.0 -- -- Acid Blue
40 -- -- 2.0 Cetyl-trimethyl ammonium bromide -- -- 2.0 Disperbyk
161 (as % solids).sup.a. 1.5 -- -- Disperbyk 2000 (as %
solids).sup.b. -- 1.6 -- Dowanol DPM -- balance -- Dowanol PMA
balance -- -- n-Butanol -- -- 10.0 Isopar H -- -- balance
.sup.a.30% solids in 6/1 methoxypropylacetate/butylglycol solvent
blend. .sup.b.40% solids in 1/1 methoxypropylacetate/butylglycol
solvent blend.
[0066] Preparation of Fixer Fluids
[0067] Fixer fluids were prepared by mixing ingredients together
according to the following recipe.
2 Fixer Formulation % weight Fixing Agent As indicated Glycerol
6.8% LEG-1 4.7% 2-Pyrolidinone 5.0% Aerosol OT 1.4% DI water
Bal
[0068]
3 Fixer PH % weight Fixing Agent Fixer 1 3.2 15.0 1,2,3,4
Butanetetracarboxylic Acid Fixer 2 6.7 15.0 Dowfax 2A1 Fixer 3 8.2
15.0 Glycolic Acid Fixer 4 2.6 15.0 Acrylic Dispersion Binder Fixer
5 7.0 15.0 Acrylic Dispersion Binder Fixer 6 8.3 12.0 Bayhdrol
PU402A Dowfax 2A1 (Dow) is a difunctional, sulfonated surfactant
Bayhdrol PU402A (Bayer) is an anionic polyester urethane resin
dispersion.
Example 1
[0069] The fixers were printed in a 1.times.3 inch block.
Immediately thereafter, ink was printed on top of the fixer and
also on an unfixed portion of the page such that there was an
additional 1.times.3 inch block of unfixed printed ink that was
used as a control. Typically, there was a period of 3 to 5 seconds
between printing the fixer and feeding the page back through the
printer to print the ink. Printing was done with an Epson 3000
printer. The print pattern was created in CorelDraw (Corel
Corporation) and the software was used to set the area fill of the
fixer and ink to 100%. Gilbert Bond (Gilbert) and Tidal MP
(HammerMill) plain paper were used as substrates.
[0070] The prints were evaluated for chroma and strikethrough using
a Minolta CM-3600 spectrophotometer (Minolta Corp., USA). Chroma
was measured on the print side of the page and the results reported
as change in chroma calculated as the ratio of chroma on the
fixed/unfixed portion of the test block. A value greater than one
for change in chroma indicates an increase in chroma for fixed ink
relative to unfixed ink and demonstrates a beneficial result for
ink/fixer combination. Chroma is summarized in the following
table.
4 Change in Chroma (fixed/unfixed) Gilbert Bond Tidal MP Fixer Ink
A Ink B Ink A Ink B Fixer 1 0.83 1.17 0.92 1.06 Fixer 2 1.01 1.09
0.97 1.05 Fixer 3 0.87 1.09 -- 1.02 Fixer 4 0.95 1.06 0.98 1.05
Fixer 6 0.95 1.03 0.88 0.99 Fixer 5 0.95 1.03 0.98 1.03
[0071] Strikethrough (S) was determined by optical density
measurement on the back side of each fixed and unfixed print area
in the test block. Specifically, the percentage change in
strikethrough was calculated according to the following
equation:
S=100.times.(1-OD.sub.f/OD.sub.u)
[0072] where OD.sub.f is the optical density of the back-side of
the fixed portion of the ink test block and OD.sub.u is the optical
density of the back-side of the unfixed portion of the ink test
block. Positive values of S correspond to the percentage reduction
in strikethrough of the fixed versus unfixed ink and demonstrates a
beneficial result for ink/fixer combination. Conversely, negative
values indicate percentage increase in strikethrough. Strikethrough
is summarized in the following table.
5 Percent Change in Strikethrough Gilbert Bond Tidal MP Fixer Ink A
Ink B Ink A Ink B Fixer 2 10.1 46.0 3.8 45.9 Fixer 1 -45.0 40.1 9.2
38.7 Fixer 3 7.7 35.0 -26.5 58.1 Fixer 6 20.5 26.3 -2.7 2.1 Fixer 5
-8.5 22.8 -39.8 34.2 Fixer 4 5.8 17.0 7.4 28.8
[0073] Results show an improvement in chroma and/or reduction in
strikethrough can be obtained through the use of the inventive
ink/fixer combinations. Of course, as is to be expected, some
judgment and routine optimization is needed to choose the
combinations, which are most effective. Also, although not
quantified, when strikethrough was reduced, bleed tended to
decrease and edge acuity improved.
Example 2
[0074] In this example, the inventive ink set is comprised of Ink C
and Fixer 1. In lieu of printing a sample, the fixing action was
assessed by placing a drop of Ink C on top of approximately 1 mL of
Fixer Fluid 1 without agitation. Instantly upon addition, the upper
phase of the nonaqueous ink "reacted" to form numerous, highly
localized, areas of intense blue color. This suggests that the
colorant stability had broken by contact with the fixer and, if
printed together, the colorant would become fixed on the
substrate.
* * * * *